The present invention relates to a clamping arrangement for a cutting insert and, more particularly, to a clamping arrangement including a holder blade having a key slot and a key recess for installing a cutting insert in an insert-receiving slot of the holder blade using a keying arrangement.
In cutting tools, for example turning tools such as lathes, it is now common, particularly in the metal-working industry, to provide replaceable cutting inserts, such as cemented carbide or tool steel inserts, on a toolholder. The inserts have cutting edges formed thereon and, after the cutting edges are worn, the inserts can be replaced. This avoids the expense of replacing the entire tool. Moreover, because the inserts can be made out of extremely hard materials, the toolholder can be made out of materials that are easier to machine. Many inserts, in addition to being replaceable, are indexable, meaning that the insert may have more than one working edge and, after one working edge is worn, the insert can be removed from the toolholder and indexed so that another working edge faces the workpiece.
Depending upon the cutting operation desired to be performed, the toolholder may be moved relative to the workpiece, the workpiece may be moved relative to the toolholder, or both the toolholder and the workpiece may be moved. Typically, very large forces are imposed on inserts during cutting operations, and tools and workpieces are moved at very high speeds, and it is necessary to securely fasten the inserts to the toolholder. There are various ways to clamp inserts in toolholders, including using bolts or screws extending through bores through the insert.
In applications such as turning applications, it is often desirable to have a thin insert mounted on a relatively thin toolholder to facilitate performing a cutting off or grooving operation deep into the workpiece. In applications such as these, it is often difficult if not impossible to have extensive extraneous clamping equipment for clamping of the insert to the toolholder. A common approach to clamping of inserts involves the use of a toolholder having an upper portion and a lower portion that define a slot at a forward end in which the insert is received. The upper portion may be fastened to the lower portion by means such as a bolt to form a cantilever that secures the insert in position as the bolt is turned to secure the upper portion to the lower portion. A disadvantage of such a multicomponent toolholder is that it is difficult to make the toolholder small enough for all applications.
Another technique for securing inserts to toolholder is by using a single-piece toolholder body in which an insert-receiving slot is formed. The insert-receiving slot is typically smaller in height than the height of the insert so that the upper and lower surfaces of the slot must be forced apart to permit installation of the insert. The resiliency of the toolholder body then operates to clamp the insert in the insert-receiving slot. U.S. Pat. Nos. 5,697,271 and 5,799,554 disclose a clamping device for a cutting insert in which the insert is installed in the holder blade by forcing apart a clamping jaw and a base jaw of a toolholder body using a specially adapted key that is applied through throughgoing apertures provided in the sides of the toolholder body. Because throughgoing apertures may, in certain operating circumstances, as well as during opening of the jaw, result in undesirable stress concentrations in a toolholder, it is desirable to provide an alternative structure that can provide an improved or different stress distribution.
The present invention permits providing clamping arrangements for single-piece toolholders that are quite narrow in width and that can be conveniently opened with a keying arrangement to permit installation of inserts in insert-receiving slots that results in improved or different stress distributions on the toolholder during operation of the cutting tool and during opening of the toolholder for insertion of an insert.
According to an embodiment of the present invention, a holder blade includes a body portion. The :body portion has a forward edge between a first side wall and an opposite, second side wall, an insert-receiving slot extending inwardly from the forward edge, the insert-receiving slot extending from the first side wall to the second side wall and having a height between an upper surface of the insert-receiving slot and a lower surface of the insert-receiving slot, a key slot extending inwardly from the forward edge, and a key recess. The key slot and the key recess are disposed relative to each other such that, when a key is installed in both the key slot and the key recess and turned from an at-rest position to an opening position relative to the body portion, the height of the insert-receiving slot is increased against resilient forces of the body portion to a sufficient height to install an insert for the holder blade and, when the key is returned to the at-rest position, the resilient forces cause the height of the insert-receiving slot to decrease and clamp the insert between the upper and lower surface of the insert-receiving slot.
According to another embodiment of the present invention, a clamping arrangement includes a holder blade having a body portion, the body portion having a forward edge between a first side wall and an opposite, second side wall, an insert-receiving slot extending inwardly from the forward edge, the insert-receiving slot extending from the first side wall to the second side wall and having a height between an upper surface of the insert-receiving slot and a lower surface of the insert-receiving slot, a key slot, and a key recess. The clamping arrangement also includes a key including a first shaft element, a second shaft element pivotably attached to the first shaft element, a first keying member attached to the first shaft element, at least a portion of the first keying member being receivable in the key slot, and a second keying member attached to the second shaft element, at least a portion of the second keying member being receivable in the key recess. The first shaft element and the second shaft element are pivotable relative to each other from an at-rest position in which the first keying member and the second keying member are at a first distance from each other to an opening position in which the first keying member and the second keying member are at a second distance from each other, the second distance being greater than the first distance. The key slot and the key recess are disposed relative to each other such that, when the first keying member is received in the key slot and the second keying member is received in the key recess and the key is moved from the at-rest position to the opening position, the height of the insert-receiving slot is increased against resilient forces of the body portion to a sufficient height to install an insert for the holder blade and, when the key is returned to the at-rest position, the resilient forces cause the height of the insert-receiving slot to decrease and clamp the insert between the upper and lower surface of the insert-receiving slot.
According to yet another embodiment of the present invention, a key assembly for a holder blade is disclosed. The holder blade has an insert-receiving slot extending inwardly from a front edge of the holder blade, the holder blade having a key slot and a key recess for receiving a first and a second keying member of the key assembly, the key slot and the key recess being arranged relative to the insert-receiving slot such that forces exerted on the key slot and the key recess in directions away from the insert-receiving slot cause the insert-receiving slot to become wider against resilient forces of the holder blade. The key assembly includes a first shaft element, a second shaft element pivotably attached to the first shaft element, a first keying member attached to the first shaft element and at least partially receivable in a key slot of a holder blade, and a second keying member attached to the second shaft element and at least partially receivable in a key recess of a holder blade.